The time to hold a line as a captain is about 3.5-6 years depending on your base, so expect at least that long on reserve making min guarantee and probably actually flying about 15-30 block hours a month.

Also the math is kind of up in the air right now, but you should expect about an 8-10 year flow.

Honestly if you're qualified for the direct entry Captain gig I'd try really hard to get on board with Spirit, Frontier, or Allegiant. Even if a legacy is your final goal getting an airbus type and right seat time will go a long way to get you on the hiring radar most likely before your flow date.